FR3146979A1 - Decorative lighting device. - Google Patents

Abstract

The invention relates to a light panel (10), for example a lighting panel for a false ceiling, comprising a receptacle (12) delimiting the external dimensions of the panel (10) comprising a light source (20) for lighting having a predefined emission spectrum (S), a front wall (14A) delimiting a transmission window (16) of the light emitted by the source (20) through the front wall (14A) and a decorative filter (60) illustrating an image through which the light passes. The transmission T(l) of the filter (60) at a wavelength l being given by the ratio between the intensity I(l) of the luminous flux transmitted by the filter (60) and the intensity Io of the luminous flux incident on the filter (60), the image comprises a composition of colored regions defined such that the transmission T(l) of the filter (60) is substantially constant over at least one interval (L) of wavelengths between 450 and 650 nanometers with a variation of less than 10%. Figure 3 _

Description

Decorative lighting device.

The present invention relates to the field of lighting and concerns more particularly but not exclusively a lighting panel, or more generally a panel, with light-emitting diodes for false ceilings. The invention applies more particularly but not exclusively to the lighting of interior rooms of commercial buildings. It concerns more generally the decoration of interior and exterior spaces, private and public.

In order to illuminate a room such as, for example, an office or a corridor, it is known to mount lighting panels, also called luminous panels, in a false ceiling fixed under the ceiling of the room. For this purpose, the false ceiling comprises in a known manner a structure comprising beams whose section is for example H-shaped, arranged in a horizontal grid and on which opaque panels and lighting panels are usually mounted. Each lighting panel comprises for example a square-shaped frame which is mounted on the beams and inside which the lighting elements are mounted.

The lighting industry must constantly be innovative in order to satisfy a clientele that is, generally speaking, attracted by novelty. It is thus known from the prior art to provide, for example in the false ceiling or in a vertical partition, a luminous tile or luminous panel that integrates a decorative function to create an illusion of a window. Such luminous tiles make it possible to bring well-being to waiting rooms, medical offices, relaxation areas, meeting rooms by creating an optical illusion of a roof glass style opening.

Typically, the decorative light panel comprises a receptacle delimiting the exterior dimensions of the panel and a light source having a predefined emission spectrum, a front wall delimiting a window for transmitting the light emitted by the source through the front wall and a decorative filter illustrating an image through which the light passes.

The disadvantage of decorative light panels is that the decorative filter significantly degrades the lighting conditions so that these panels are only used for decorative purposes.

Indeed, a lighting device, for example for use in a medical environment, particularly in an operating room, must allow a surgeon to operate in good conditions. Thus, such a lighting device must allow a surgeon to correctly distinguish between different types of biological tissues.

To achieve this, the lighting device must comply with certain standards and produce a generally white light that has a color rendering index (CRI) between 85 and 100. In addition, the color temperature of the light produced by the lighting device must be between 3000 K (warm tones) and 6700 K (cool tones), according to the IEC 60601-2-41 standard, to allow the surgeon to effortlessly distinguish small color differences.

By "color temperature" of a light is meant the evaluated equivalent color temperature, as well known from the spectrum of light in a reference color diagram of the International Commission on Illumination.

The invention aims in particular to propose a decorative light panel which can be used for lighting purposes, in particular professional lighting.

Description of the invention

The invention relates in particular to a light panel, for example a lighting panel for a false ceiling, comprising a receptacle delimiting the external dimensions of the panel comprising a light source for lighting having a predefined emission spectrum, a front wall delimiting a window for transmitting the light emitted by the source through the front wall and a decorative filter illustrating an image through which the light passes, characterized in that , the transmission T(l) of the filter at a wavelength l being given by the ratio between the intensity I(l) of the luminous flux transmitted by the filter and the intensity Io of the luminous flux incident on the filter, the image comprises a composition of colored regions defined such that the transmission T(l) of the filter is substantially constant over at least one predefined interval of wavelengths extending at least over a range of 450 to 650 nanometers, preferably between 400 and 800 nanometers with a variation of less than 10% relative to an average spectral transmission value Tm calculated on this interval.

Thanks to the invention, the mixing of colours results in the emitted light having unchanged spectral characteristics in the predefined wavelength range for an observer located at a predetermined distance from the panel.

In a preferred embodiment of the invention, the variation is less than 5%.

In a preferred embodiment of the invention, the wavelength range substantially corresponds to the emission spectrum of the light source such that the color rendering index with the filter is substantially identical to the color rendering index without the filter, for an observer located at a predefined distance sufficient to allow mixing of the light coming from the filter.

In a preferred embodiment, the receptacle comprises a reflective back wall and a peripheral frame defining side walls, at least one side wall of which carries a row of light-emitting diodes forming the source.

In a preferred embodiment, the front wall carries the decorative filter.

In a preferred embodiment of the invention, the wavelength range is defined such that the range extends over wavelengths of the light emission spectrum for which the relative intensity emitted by the light source is greater than 20%, preferably 10%.

In a preferred embodiment, the decorative filter is formed by a decorative film attached to a diffusion plate or by a decorative plate made of a translucent diffusing plastic material.

In a preferred embodiment, the decorative film is produced by color printing applied to a diffusing plate or by screen printing.

In a preferred embodiment, the image of the decorative filter is delimited into several colored spatial regions of dominant blue, green, white representative of a natural decor.

In a preferred embodiment, the decorative filter image comprises a composition of areas of green vegetation, areas of blue sky and areas of clouds.

The invention also relates to a false ceiling according to the invention, characterized in that it comprises a plurality of panels according to the invention, arranged so as to form a decorated ceiling.

The invention will be better understood and its advantages will appear better, on reading the detailed description which follows, of embodiments represented as non-limiting examples. The description refers to the appended drawings in which:

There represents a false ceiling in which the light panel according to the invention is mounted.

There represents a perspective view of the panel of the .

There represents an exploded perspective view of the panel of the .

There represents a graph representing the emission spectrum of the light source as a function of wavelength.

There represents an illustration of a front view of a decorative panel according to the invention.

There schematically represents a sectional view of a diffuser carrying a decorative filter of the panel of the .

Detailed description of the invention

It is schematically represented on the a light-emitting diode panel designated by the general reference 10. In the example illustrated, the panel 10 comprises a front lighting face intended to be oriented towards the ground and a rear face intended to be oriented towards the support to which the panel 10 is fixed, for example a false ceiling 100.

The panel 10 also comprises a receptacle 12 delimiting the external dimensions of the panel 10 and comprising at the front a light-emitting front wall 14A delimiting a light-emitting window 16. On the , we see that the front wall 14A generally delimits the lighting window 20 in a general plate shape.

In this example, the panel 10 further comprises a rear wall 14B opposite the front wall 14A which is generally either intended to extend inside an opening in a false ceiling 100 or intended to be fixed directly to the ceiling. Furthermore, the panel 10 further comprises a peripheral wall or peripheral edge 18 connecting the two front 14A and rear 14B walls together. Thus, the panel 10 delimits a housing, for example of generally square shape, as illustrated in the .

For the purposes of the present invention, a panel or slab is understood to mean a product whose width and length are of the same order of magnitude, this order of magnitude being much greater than that of the height. The panel may optionally have curved, concave or convex front and rear faces. In the example illustrated, the panel 10 has a generally square shape but of course the panel may alternatively be indifferently round, oval, rectangular or polygonal in shape.

In the illustrated example, the peripheral wall 18 of the receptacle 12 comprises a peripheral aluminum frame, for example formed by the joining of aluminum profiles 18A, 18B, 18C, and 18D.

In order to provide a conventional lighting function, the panel 10 comprises a light-emitting diode lighting source 20. This lighting source 20 is housed inside the panel 10 and is capable of illuminating through the front wall 14A via the window 20. For the purposes of the invention, visible light means light with wavelengths between approximately 400 nanometers and 800 nanometers. As an example, the following figure shows: , the emission spectrum of the lighting source 20 as a function of the wavelength.

Preferably, the luminaire 10 comprises a reflector 30 arranged in the receptacle 12 and provided with a reflecting surface internal to the receptacle 12 configured to reflect the light emitted by the source 16 mainly in the direction of the lighting window 20. In the example illustrated, the reflector 30 has the general shape of a plate and forms the back wall 14B of the panel 10.

On the , preferably, the lighting source 20 is arranged inside the panel 10 along an edge of the peripheral wall 18 in order to illuminate through the panel 10.

Furthermore, for example, the luminaire 10 also comprises a guide 40 for guiding the light beam emitted by the lighting source 20 in a transverse direction of the panel 10 by multiple reflections inside the guide 40 and configured to allow the light to exit from the guide 40 towards the reflector 30.

Preferably, the guide 40 is for example in the form of a guide plate. Preferably, the lighting source 20 comprises a plurality of light-emitting diodes, arranged for example in the form of one or more strips of light-emitting diodes. The strip of diodes can for example be arranged on an edge of the peripheral edge 18 of the panel 10.

For example, the panel 10 may comprise a single strip of light-emitting diodes, preferably housed longitudinally in one of the profiles 18. In this case, opposite the strip of light-emitting diodes, a reflective strip is affixed, for example by gluing, to the opposite edge of the panel 10. Optionally, the panel 10 may comprise more than one strip of light-emitting diodes, for example two strips arranged on two opposite sides of the panel 10.

Furthermore, for example, in order to allow light to exit the guide 40, preferably, the guide plate 40 comprises a whole series of light exit points (not visible in the figures) which are distributed on a face of the guide plate 40 arranged opposite the reflector 30. This series of points has for example a distribution in the form of a network formed on one of the faces of the guide plate 40, here the back face. Advantageously, the distribution of the points is such that the light which exits the optical guide plate 40 has a homogeneous intensity over the entire surface of the panel 10.

These points can be formed for example by openings made in the guide plate 40 or by scratches or by any irregularities allowing an exit from the light guide 40. The light emitted along one of the edges of the guide plate 40 is guided inside the optical guide by multiple reflections and able to exit the guide plate 40 through these points.

This series of points can for example be formed by a flexible polymer coating bonded directly to one of the faces of the guide plate 40. In this case, the distribution of the points can be symmetrical with respect to a vertical plane comprising an axis passing through the middle of the panel 10, in order to ensure a generally uniform distribution of the light intensity. For example, it is possible to provide points that are smaller near the lighting source 20 and larger as one moves away from it. Alternatively, it is possible to vary only the density of light output points and no longer the dimension of the points. As is apparent from the detailed description of the luminaire 10, in this preferred embodiment of the invention, the light beam emitted by the light source 20 undergoes several reflections, in particular inside the guide 40 (multiple reflections on internal walls of the guide) and on the internal reflective surface of the reflector 30.

Preferably, the luminaire 12 also comprises a diffuser 50, for example extending substantially at the level of the lighting window 16 to provide an improvement in the homogeneity of the lighting in visible light.

According to the invention, the front wall 14A delimits a transmission window 16 of the light emitted by the source 20 through the front wall 14A and a decorative filter 60 illustrating an image through which the light passes.

In particular, according to the invention, the image of the filter 60 comprises a composition of colored regions defined such that the transmission of the filter 60 is substantially constant over at least one predefined interval of wavelengths extending at least over a range of 450 to 650 nanometers with a variation of less than 10%, preferably 5% relative to an average value of spectral transmission Tm over the predefined interval. Preferably, the interval can extend within a range of 400 to 800 nanometers.

Classically, a color image is a matrix of points or pixels M arranged in two dimensions and each pixel M has a horizontal coordinate x and a vertical coordinate y. Each pixel M of a color image is a triplet (R, G, B) of values ranging from 0 to 255 (256 different values), the values being for example coded on 8 bits. For each pixel M, a light intensity (brightness parameter) can be associated and a wavelength.

The transmission of the filter 60 for a wavelength l is given by the ratio between the intensity I(l) of the luminous flux transmitted by the filter 60 and the intensity Io of the luminous flux incident on the filter 60.

In order to determine the intensity of the luminous flux I(l) for a given wavelength, the surface of the filter 60 is for example cut into a plurality of unit elements M of coordinates (x, y) emitting an intensity dI(M, l), the intensity I(l) being equal to the sum over the entire surface of the filter 60 of the intensities dI(M, l).

Io being the intensity emitted by the source 20 without the filter and I(l) being the intensity emitted over the entire surface after passing through the filter 60, and T(l) the ratio between I/Io or spectral transmission. The spectral transmission T(l) for a given wavelength can then be expressed as follows:

According to the invention, over the wavelength range, the spectral transmission is substantially constant.

Preferably, the color image of the filter 60 is processed using a pixel-by-pixel image processing algorithm such as that described below.

Initially, preferably a color image, such as that shown in the , which visually presents a balance of colors, for example a balanced composition of green 60A, blue 60C and white 60B, is selected.

Then, in a first step, an interval L of wavelengths is predefined, for example with respect to the spectrum of the light source 20.

In a second step, the elementary spectral transmission dT(l) per pixel is calculated from a correspondence table allowing a relationship to be established between the values of the triplet associated with each pixel, representative of a light intensity, and a wavelength l corresponding to the color of the pixel.

As a first approximation, the spectral transmission T(l) will be obtained by summing over the entire surface of the filter 60 the elementary spectral transmissions dT(l) defined per pixel.

In a third step, an average value Tm of spectral transmission of the image is calculated over the predefined wavelength interval L.

Finally, the spectral transmission values T(l) which have a deviation greater than 10%, preferably greater than 5%, compared to the average spectral transmission value Tm are modified (the deviation is reduced compared to the average value Tm) by optimizing the values of the triplet of each pixel. This makes it possible to obtain a spectral transmission which is substantially constant over the interval L.

Preferably as illustrated in the , the front wall 14A carries the decorative filter 60. For example, the decorative filter 60 is formed by a decorative film applied to a diffusion plate 50 ( ) or by a decorative plate made of a translucent diffusing plastic material.

In the example described, the decorative film 60 is produced by color printing applied to a diffusing plate 50 or by screen printing. Of course, other techniques for printing an image can be carried out without departing from the scope of the invention.

We will now describe the main operating aspects of the light panel according to the invention with reference to Figures 4 to 6 in particular.

There represents an example of an emission spectrum S of a light source 20, that is to say the relative intensity emitted by the source 20 as a function of the wavelength of the light. In this , we can note the presence in the emission spectrum of a main blue peak of short wavelengths between approximately 430 nm and 480 nm centered around 450 nm and of a secondary peak between approximately 450 nm and 700 nm.

The wavelength interval L is illustrated in this same figure and extends between 430 nm and 700 nm in order to cover both the main and secondary peaks. Preferably, the wavelength interval L extends over wavelengths of the light emission spectrum for which the relative intensity emitted by the light source 20 is greater than 20%.

The image of the decorative filter 60 is delimited into several spatial regions 60A, 60B, 60C colored with a dominant blue, green, white color representative of a natural decor. For example, as illustrated in the , the image of the decorative filter 60 comprises a composition of green plant areas 60A, blue sky areas 60C and cloud areas 60B.

Over the interval L, thanks to the invention, the spectral transmission T(l) is substantially uniform. Despite the decorative filter 60, an observer located for example 1 meter from the panel 10 observes a beam of light of substantially white color, with a color rendering index almost identical to that of the light source 20 before the filter 60. Indeed, at a distance of 1 meter, the light beams from the different colored regions 60A, 60B, 60C of the filter 60 mix so as to form a homogeneous light having a spectral distribution almost unchanged compared to the light source 20, thanks to the uniformity of the filter 60.

Of course, other embodiments are conceivable without departing from the scope of the invention. Thus, various modifications can be made by those skilled in the art to the invention which has just been described by way of example.

Claims (10)

Light panel (10), for example a lighting panel for a false ceiling, comprising a receptacle (12) delimiting the external dimensions of the panel (10) comprising a light source (20) for lighting having a predefined emission spectrum (S), a front wall (14A) delimiting a transmission window (16) of the light emitted by the source (20) through the front wall (14A) and a decorative filter (60) illustrating an image through which the light passes, characterized in that , the transmission T(l) of the filter (60) at a wavelength l being given by the ratio between the intensity I(l) of the luminous flux transmitted by the filter (60) and the intensity Io of the luminous flux incident on the filter (60), the image comprises a composition of colored regions (60A, 60B, 60C) defined such that the transmission T(l) of the filter (60) is substantially constant over at least one predefined interval (L) of wavelengths extending at least over a range of 450 to 650 nanometers, with a variation of less than 10% relative to an average spectral transmission value Tm calculated over this interval (L). Panel (10) according to the preceding claim, in which the variation is less than 5%. Panel (10) according to any one of the preceding claims, in which the wavelength interval (L) is defined such that the interval (L) extends over wavelengths of the light emission spectrum for which the relative intensity emitted by the light source (20) is greater than 20%, preferably 10%. Panel (10) according to any one of the preceding claims, in which the wavelength interval (L) corresponds substantially to the emission spectrum of the light source (20) so that the colour rendering index with the filter (30) is substantially identical to the colour rendering index without the filter (30), for an observer located at a predefined distance (D) sufficient to allow mixing of the light coming from the filter (60). Panel (10) according to the preceding claim, in which the receptacle (12) comprises a reflective back wall (14B) and a peripheral frame (18) delimiting side walls (18A, 18B, 18C, 18D), at least one side wall (18A, 18B, 18C, 18D) of which carries a row of light-emitting diodes forming the source (20). Panel (10) according to the preceding claim, in which the front wall (14A) carries the decorative filter (60). Panel (10) according to the preceding claim, in which the decorative filter (60) is formed by a decorative film attached to a diffusion plate (50) or by a decorative plate made of a translucent diffusing plastic material. Panel (10) according to the preceding claim, in which the decorative film (60) is produced by color printing applied to a diffusing plate (50) or by screen printing. Panel (10) according to any one of the preceding claims, in which the image of the decorative filter (60) is delimited into several spatial regions (60A, 60B, 60C) colored with a dominant blue, green, white color representative of a natural decor. A panel (10) according to any preceding claim, wherein the image of the decorative filter (60) comprises a composition of areas of green vegetation, areas of blue sky and areas of clouds.